1. Field of the Invention
The present invention relates to the assembly of solar cells into an array for the conversion of solar energy from a large area concentrator, typically a parabolic reflector or the optical equivalent constructed of mirror segments, either flat or figured, into electricity. More specifically it applies to the methodology of maximizing the fraction of sunlight captured by the concentrator that is converted into electrical power.
2. Prior Art
Traditional one sun solar panels are made by simply bonding solar cells to a substrate, such as aluminum honeycomb panels, and interconnecting the cells with metal ribbons front to back. The cells are spaced slightly apart to allow the interconnecting ribbons to pass between the adjacent cells. Furthermore the entire front surface area of the cell may not be active due to the necessity of a front surface contact to which the ribbons are bonded. The space between cells active areas are of little consequence, since sunlight bathes the entire surface of the earth more or less uniformly, and the power output of a loosely packed panel will be the same as a closely packed one. Excessive spacing might lead to a slightly higher manufacturing cost due to a larger than necessary substrate, and a marginally lower system efficiency, but from a practical standpoint packing density is not a major concern for one sun solar panels.
Concentrator PV systems, systems which use ancillary optics to intensify the light striking the solar cell, make the available illuminated area a cost driven commodity since the light striking the solar cells is no longer free, but has been preconditioned by costly hardware. If the system uses multiple concentrator elements, such as a parquet of Fresnel lenses, the output of a single concentrator element can be directed to a single cell, and light utilization approximates 100%. If the concentrator consists of one or more large concentrating elements, such as a parabolic dish, or optical equivalent packing density becomes very important. Every bit of concentrated sunlight that falls between the active areas of solar cells is lost, resulting directly in reduced system efficiency.
To further compound the problem in dense arrays, in addition to the solar cell area lost to top surface contacts, most solar cells require individual diode protection across each cell in an array. These diodes are discrete components and require some physical area on the substrate for mounting. Heretofore the only solution to this problem has been to utilize only back contact cells, packed as tightly as possible and use diode protection only across large segments of the cells which can be reached through connections at the periphery of the field of solar cells.